The present invention relates to the improved control of fibers in apron drafting systems of machines used in the process of spinning, especially the spinning frame and the roving frame.
As is already known, the roving of sliver which feeds the machine is subjected to drafting in one or more consecutive zones, which includes a prior back drafting between several pairs of rolls, and a front drafting between several other pairs of rolls. There is a pair of front rolls between which the roving or sliver is finally drafted and guided between both pairs of rolls by means of sundry aprons, both top and bottom constituted of corresponding elements in the style of conveyors.
Each type of fiber presents determined lengths, and in order to avoid breakage of the fibers constituting the roving or sliver, the distance between the pairs of rolls had to be adjusted. More particularly, the distance between the front pair of rolls and the point or face of contact between the top and bottom aprons need be adjusted due to the fact that the effect of the pairs of rolls is to nip (or pinch) the surface of the roving fibers.
Up to the present time, in order to avoid this breakage of the fibers, obtain the maximum control of the fibers, and attain perfect uniformity of the yarn, a method has been used of elevating or lowering the top apron by the front part. By this, a separation or space is produced between the top and bottom aprons which does not permit adequate control of the roving fibers.
The present invention provides improved control of the fibers and permits obtaining different intensities of control of the fibers at different points within the drafting zone. This permits adjustment of the control of the fibers in accordance with required conditions. The control points can be adjusted independently in accordance with the type and length of fibers, permitting numerous combinations to obtain an effective control for all types of fibers.